This project proposes to investigate mechanism of the orally induced immune response as it affects periodontal disease. Specific aims of the proposal include: 1) The investigation of potential differences in antigen access to secretory and systemic lymphoid tissue after injection or oral administration of antigen in soluble or particulate forms 2) An examination of the role of serum IgG or dimeric IgA antibody in the tolerance or suppression observed after oral administration of antigen 3) The investigation of the potential role of IgG or IgA antibody-antigen interactions affecting the oral induction of salivary IgA antibody to an unrelated antigen 4) An examination of the tolerance or suppression of the systemic immune response produced after oral administration of antigen and the effect of this suppression on the loss of bone and on the immune response in gnotobiotically infected rats. Specific methodology employed will include the following biochemical and biological techniques: gel filtration, ion exchange chromatography, enzyme linked immunosorbent assay, i.v. infusion of passive antibody, radioiodination of antigens and gamma counting, immunoelectrophoresis, fluorescinated antibody labeling, germ-free animal work and other techniques used in the preparation of antigens and additional antisera. It is hoped that this proposed project will develop information which will contribute to a greater knowledge of secretory immune system stimulation and suppression by oral administration antigen. The direct effect of oral administration of a bacterial antigen on immune suppression, inflammatory infiltrate and on bone loss in gnotobiotic rats should elicit information of direct relevance on the use of the secretory immune system to prevent or control periodontal disease.